Benchmark: Array.splice(0, N) vs Array.length === N

Script Preparation code:

var arr = Array.from(Array(100).keys());

Tests:

`Array.slice(0, N)`
arr.length = 20;
`Array.length === N`
arr.length === 100;

Rendered benchmark preparation results:

Suite status: <idle, ready to run>

Previous results

Test case name	Result
`Array.slice(0, N)`
`Array.length === N`

Fastest: N/A

Slowest: N/A

Latest run results:

Run details: (Test run date: 5 months ago)

User agent: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/142.0.0.0 Safari/537.36

Browser/OS: Chrome 142 on Linux

View result in a separate tab

Test name	Executions per second
`Array.slice(0, N)`	29867256.0 Ops/sec
`Array.length === N`	153646384.0 Ops/sec

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):

LLMs can make mistakes. Check important info.

Let's break down the benchmark and explain what's being tested.

**Benchmark Definition**
The benchmark is testing two approaches to measuring array length:

1. `Array.splice(0, N)`: This approach uses `splice()` method to remove the first `N` elements from an empty array, effectively setting its length to `N`.
2. `Array.length === N`: This approach checks if the length of the array is equal to `N` directly.

**Options Compared**

* `Array.splice(0, N)` vs `Array.length === N`
* The first option uses a method call (`splice()`) to modify the array's length.
* The second option uses a simple property access (`length`).

**Pros and Cons of Each Approach**

* **`Array.splice(0, N)`**
	+ Pros:
		- Works on all browsers, including older ones that may not support `Array.length === N`.
		- Can be used to remove elements from an array.
	+ Cons:
		- Modifies the original array.
		- May have performance implications due to the method call and potential reallocation of memory.
* **`Array.length === N`**
	+ Pros:
		- Directly checks the length property, which is usually fast.
		- Does not modify the original array.
	+ Cons:
		- Only works on modern browsers that support `Array.length === N`.
		- May require additional logic to handle edge cases or errors.

**Library and Special JS Features**
None of the benchmark uses any external libraries, and it does not test special JavaScript features like async/await, promises, or ES6 classes. The focus is solely on the basic length property comparison.

**Alternatives**

Other alternatives for measuring array length include:

* Using `Array.from()` with an empty iterable to create a new array of a specific length.
* Using `Object.create(null)` and then setting the `length` property directly on the object (although this method is not recommended due to potential security concerns).

It's worth noting that in modern JavaScript, the `Array.length === N` approach is generally considered the most efficient and idiomatic way to check an array's length. However, older browsers may require the use of `Array.splice(0, N)` as a fallback.

Related benchmarks:

Array.splice(0, N) vs Array.length === N (version: 0)

Comparing performance of: `Array.slice(0, N)` vs `Array.length === N`

Created: 2 years ago by: Guest

Jump to the latest result

`Array.slice(0, N)`

`Array.length === N`

Suite status: <idle, ready to run>

Fastest: N/A

Slowest: N/A

Autogenerated LLM Summary (model llama3.2:3b, generated one year ago):